The principal effort was concerned with the galactosyltransferase which with alpha-lactalbumin are responsible for the biosynthesis of lactose. Multiple forms of the galactosyltransferase are catalytically active to the same extent and have molecular weights of 55,000 and 44,000. Preliminary evidence indicates that the lower molecular form may arise from proteolysis of the higher molecular weight form. The galactosyltransferase contains two types of carbohydrate side-chains, one of the serine type and the other of the asparagine type. Present studies are concerned with elucidation of the multiple forms and carbohydrate structure of the galactosyltransferase.